1. Field of the Invention
The invention relates to an exhaust system. The exhaust system is intended, for example, for a car but may also be used for another motor vehicle--for example a truck or bus. The internal combustion engine may consist of a gasoline or diesel engine.
2. Description of the Prior Art
The engine housing of the internal combustion engine of a motor vehicle is usually held on the vehicle body by retaining means in such a way that it is slightly mobile, elastically mounted and damped with respect to vibration. When the motor vehicle is used, rapid load changes and rapid changes in the speed of the engine shaft and/or of the torque output by said shaft cause rapid changes in the power of the internal combustion engine. These may in turn give rise to movements, namely approximately rotation and/or swivelling of the engine casing about a virtual axis of rotation and/or pivot axis. Furthermore, the internal combustion engine produces vibrations or oscillations of the engine casing. These may cause, inter alia, periodic swivelling back and forth or torsional oscillations about the virtual axis of rotation and/or pivot axis. The virtual axis generally does not coincide with the geometric axis of rotation of the engine shaft and is, for example, offset from the axis of rotation of the engine shaft and approximately parallel to said axis. In the case of the swivelling caused by power changes and/or by vibrations, the engine casing may be swivelled back and forth or rotated through angles which are, for example, up to about 5.degree..
Known exhausts have an exhaust section which is rigidly connected to the engine casing and is connected via a flexible pipe member to at least one catalytic converter and/or silencer arranged downstream of said pipe member and having a casing. If the exhaust section located downstream of a flexible pipe member contains a plurality of casings, a flexible pipe member is sometimes also arranged between the successive casings. The flexible pipe members have, for example, a bellows. The exhaust section located downstream of a flexible pipe member is usually held displaceably on the vehicle body by, for example, retaining means having rubber rings.
During operation, the exhaust section connected rigidly to the engine housing is concomitantly moved by the swivelling engine casing and, when connected to the (first) flexible pipe member, executes swivelling movements whose arc lengths are--depending on the distance from the virtual axis--for example several centimeters and cause considerable deformations of the bellows. When these movements occur, the distance of the entrance of the bellows from the (first) casing is usually changed. In general, the result of this is that the bellows is not only frequently bent but at the same time is also alternately compressed and extended and frequently also subjected to shear movements. Bellows may withstand a very large number of bending movements without damage. Furthermore, small changes in the length of the bellows are also permissible. However, length changes and especially shear movements occurring simultaneously with bending movements give rise to considerable stresses in the bellows and shorten their service life.